In some places the water supply has so much calcium and other dissolved minerals that when the water is heated, solid precipitates form and accumulate as scale inside the water heater and hot water pipes. Scale accumulation inside the water heater typically reduces the life of large tanks, such as used by office buildings and apartment buildings with central hot water systems, from 5-8 years to 2-5 years. Domestically, scale buildup is not as much of a concern; household water heaters and pipes last 10-20 years before scale becomes a problem, even when the water supply is very hard. However, many households still purchase water softeners. In areas where the water supply is hard, apartment complexes with central hot water supplies need to de-scale the hot water pipes about once every 6 years, costing up to $30,000 depending on the amount of damage to the pipes. Typically, iron pipes can be de-scaled about three times before they must be replaced.
A secondary problem is scale buildup in the water heater. One water heater manufacturer offers a “turbo” model which uses small orifices on the input pipe to create turbulence inside the tank. The concept is to flush out scale buildup with the turbulence. Unfortunately, it is cheaper to keep the scale in the water heater; a commercial size domestic water heater costs about $3,000 (including labor) to replace, while de-scaling the pipes is much more expensive.
Current water treatment methods are too effective and too costly for applications where the objective is reducing scale buildup in the water heater and hot water pipes. Ion exchange water softening systems, such as supplied by Culligan, are both expensive and costly to maintain. These systems require regular maintenance and when used to treat large quantities of water the upkeep makes them economically unfeasible.
Another treatment technique is reverse osmosis. Reverse osmosis systems can treat large quantities of water, as in semiconductor factories, and purify water through a reverse osmotic membrane. In addition to filtering out the carbonates that cause scale, these systems also remove heavy metals and biological contaminants. Reverse osmosis systems are more expensive than ion exchange systems and are directed towards improving water quality rather than only removing the chemicals that become scale. Both ion exchange and reverse osmosis systems remove scale, but at a cost where it is cheaper for office buildings and apartment complexes to de-scale and replace hot water pipes than purchase and maintain a water softener.
U.S. Pat. No. 6,416,673 and others, by Plester, and assigned to The Coca Cola Company, describe a filtering system consisting of a heater, filter and cooler; implemented to treat water for a soft drink dispenser. Plester's preferred method of removing scale from hot water is a filter made of polyester fiber mesh. Plester's patent differs from this invention in that the application is specifically for filtering water for a soft drink dispenser; a low volume application requiring a high removal efficiency. By comparison, this invention is for domestic or commercial hot water supplies with 10 to 10,000 times more volume, is less efficient, and uses granules or loose mesh material rather than a filter to remove the precipitate. There is no interest in improving taste, removing gasses, or sterilization as is desired for the Coca Cola application.
Other patents discovered in a patent search cover hot water tanks, heaters, valves, filters, additives, hardness sensors, control circuits, ionic exchange softeners, reverse osmosis, and stills. None of these devices are the same as this invention.